Experimental study of directivity effect of rock interface under Brazilian splitting

A series of Brazilian split tests on rock-cement interface considering the effect of interface orientations were conducted to investigate the influence of hard rock-soft rock interface direction on failure behavior. The tensile strength for different interface orientations was obtained and failure mechanism of the interface was analyzed by the particle flow code PFC2D. The measured tensile strength increases as the interface-loading angle increases. The measured tensile strength can be considered to be equivalent to that of the interface if the interface orientation is parallel to the loading direction, because tensile failures occur along the interface. Mixedmode failures occur if the interface is not parallel to the loading line. In addition, another series of Brazilian tests were conducted to investigate the influence of the interface tensile strength on failures by increasing the cement dosage and roughening the rock surface. Based on the results, a diagram of the failure mode distribution marked with the typical failure patterns from the Brazilian test results for the rock-cement interface was developed. These findings provide a better understanding of the failure modes of the hard rock-soft rock interface.